The research proposed here will investigate the effects of acute and chronic morphine administration on the three parameters of brain stimulation reward (BSR) in the ventral noradrenergic bundle (VNB) of albino rats. The parameters of brain stimulation reward to be examined are: 1) the rate of lever-presses for electrical brain stimulation, 2) the threshold (stimulating current) of reinforcement and 3) the impedence to the stimulating current. The VNB was chosen because recently it has been found that; a) this pathway supports vigorous BSR (Ritter and Stein, 1974) and b) lesion of this pathway with the selective catecholamine neurotoxin 6-hydroxydopamine reduces opioid self-administration, tolerance, and physical dependence (Lewis, Costa, Jacobowitz, and Margules, 1976). Rats with chronic implants of bipoplar platinum electrodes in the mesencephalic projection of the VNB will learn to lever press for electrical brain stimulation. The three parameters of brain stimulation will be determined using computer controlled and monitored brain stimulation equipment. Experiment 1 examines the effects of acute and chronic morphine injections at low (4mg/kg) and high (12 mg/kg doses on the BSR parameters. Symptoms of physical dependence will be observed during chronic administration and correlated with changes in BSR parameters. Experiment 2 will determine if the observed changes in BSR are reversed by naloxone, a narcotic antagonist. Experiment 3 will determine the effects of prolonged abstinence in previously dependent animals on BSR. The changes in BSR parameters during acute and chronic opiate injections; a) should prove informative in understanding the basis of opiate's reinforcing properties; b) may show reliable changes with the onset of tolerance and physical dependence.